Umm...the episode called...'Scorched Earth' in Season 4, they have a disagreement, that ends in Sam actually doing what he wanted, and also in 'The Light' when they kinda argued on the beach...oooh and '2010' when she wanted him to help them. they didn't really fight, but he was rather bitter.

Not quite sure but I think they have a bit of a fight in the episode where Sam's Dad dies. I have this image in my head of Sam shouting and crying then Jack hugs her in my mind and can't place it. Sorry. If it comes to me I'll post!